The present invention broadly relates to a photoelectric smoke detector and, more specifically, pertains to a new and improved construction of a small-size or miniature photoelectric smoke detector.
In its more particular aspects, the present invention specifically relates to a new and improved construction of a photoelectric smoke detector which is equipped with a light emitter for radiating light into a measuring space and a light receiver for detecting scattered light caused by the entry or presence of smoke in the measuring space.
Dark chambers of conventional photoelectric smoke detectors have a complicated labyrinth construction or double covers to prevent the environmental light from entering the dark chamber but to facilitate entry of smoke into the same, see, for example, U.S. Pat. No. 4,596,465, granted June 24, 1986, and U.S. Pat. No. 4,216,377, granted Aug. 5, 1980.
However, such photoelectric smoke detectors with the above-mentioned dark chamber construction, being large in size, are not suitable for use as photoelectric smoke detectors to be built-in into equipment such as electronic computers or to be installed in lavatories in aircraft. These photoelectric smoke detectors also have the disadvantage that miniaturization thereof by merely reducing the size of their dark chambers results in lowering the SN ratio.